Below the Surface
by Lilis the pokemon lover
Summary: Mabel Pines did not know what to expect. She had went on a search for her missing family member only to fall into the Underground, which was full of monsters. Follow her as she embarks on an accidental journey, filled with determination.


Prologue

A/N: Okay, this story may be a crossover, but this chapter focuses on the Gravity Falls characters, so if you're here for the Undertale content, sorry but you'll have to read this chapter or you'll be confused. By the way, there are a lot of time skips in this story, so don't be shy to ask if you don't understand. Let's just get on with the story. Notes are at the end. Read and review, please!

Warning: Major death, suicidal thoughts

-0-0-

The waiting room was filled with silence, with nobody except the teenage girl occupying the vicinity. Mabel sat quietly, fidgeting in her seat. It has been over two hours but her great-uncle, Ford, had not arrived to pick her up. It had been about a year since she and Dipper, her twin brother, had bid farewell before she went back to California while he stayed with Ford for his apprenticeship in paranormal investigation. They had barely talked during Stan's funeral, which made Mabel wonder if her brother had changed. She yearned to see her only living family members after her parents had perished in a tragic car accident.

The young girl's mind wandered towards her brother as he scratched Waddles, her pet pig. Only Ford had showed up weeks ago at the younger twins' parents' funeral, claiming that Dipper had refused to come along. This made Mabel felt as if her only trusted companion did not care off their parents. But she had her hopes up since Ford had stated that he was bringing along her twin to pick her up in his phone call earlier that day.

 _Maybe I should just calm down and do something to occupy myself. Like, it's not as if they wouldn't arrive!_ Mabel thought, flipping through a pile of outdated newspapers on a cabinet near her.

"HAH! YOU THINK THE PINES ARE INVINCIBLE? I CURSE THE PINES! EACH EVERY ONE WILL DIE! ONLY ONE LUCKY BUT RANDOM PINES WILL SURVIVE! LET'S SEE WHO THEY ARE!"

Mabel winced as the voice of the perished demon, Bill, echoed in her head. She knew that he was behind her parents and Stan,s death, no matter how much she denied it. Nobody from the same family would suddenly die coincidentally. A curse that was placed on her family by Bill with his dying breath. If she had not made a deal with him in the first place, Weirdmegaddon would not have happened. Bill would not have turned real, and their family would not be cursed. As much as she tried to push it towards the back of her mind, the girl feared that she would lose her brother or her great-uncle. If either of them were to die, she hoped that it would be her. She does not deserve to live after causing such catastrophe to Gravity Falls.

With a sigh, the teenager pulled out a crinkle newspaper from the pile, reading the headlines. It was dated years ago, the article on the front page warning that people should avoid hiking Mt Ebott, claiming that seven children had went missing in the past years. Mabel frowned. Why would six children _even_ climb the mountain? She was curious of where it was located.

"Mabel?"

At the mention of her name, Mabel looked towards the door, smiling. Ford walked towards her, sporting his favourite trench coat, with Dipper trudging behind him. Dipper had changed his usual clothing to a shirt under his blue jacket with brown pants and glasses. She lunged towards Dipper, wrapping her arms around her twin. He stiffly stood his place, not returning the gesture. Waddles just snorted as it observed the scene.

"It's been a while Dipper!" Mabel said, letting go as she smiled at Ford.

"Yeah. So are we going back or what?" Dipper bluntly replied, tapping on his watch.

"Dipper, at least welcome your sister. She's been through a lot," Ford reminded, ruffling Mabel's hair, ignoring his nephew rolling his eyes.

"So, are you ready to go back to Gravity Falls?" the paranormal researcher inquired.

"Great-uncle Ford, of course she's ready! Her luggage is there!" Dipper snapped.

Ford have the teenage boy a death glare, causing him to mumble something inaudible. Mabel looked over at the researchers quizzically. She knew Dipper was stubborn at times but why was he acting so weirdly, even towards Ford, his idol? Maybe things happened between them, but Mabel decided not to dwell deeper into it. Like the saying goes, curiosity kills the cat.

-0-0-

It has been months since she moved in at Gravity Falls and Mabel had had enough of Dipper. She had been observing her brother for months and found out several things. Like she had suspected, Dipper had an argument with Ford during an expedition, with the latter barely escaping danger. However, that was not the only issue. She had been asking personal friends- Wendy, Soos and other trusted residents- and soon took notice that Dipper was not hanging out with anybody except some students his age. Being his sister, she stalked him and saw him loitering with the stated group,

"I'm going to ask Dipper if he has anything to talk to me about those teenagers and why he is acting so strangely," Mabel muttered, knocking on the door of the attic, which.was now Dipper's personal room.

That was a shuffle before the door swing open, Dipper moodily looking at Mabel. Arms akimbo, Mabel raised her eyebrows in an attempt to look intimidating.

"Mabel, whatever it is, make it brief because I have to meet up with my friends on time," Dipper bluntly ordered, sighing exasperated.

" _What?_ But it's _already_ seven p.m. and you _still_ want to go out? You didn't even _tell_ me!" Mabel exclaimed as Dipper out on his jacket.

" _So?_ I have my own life. Did you forget that things change? You should just grow up and leave me alone," Dipper hissed, pushing the teenage girl aside.

"Dipper, why are you acting as if we aren't even a family? You just go and hang out with this random people everyday! I'm your sister, for goodness sake!"

"You don't hang out with anybody anymore! Not with Grunkle Ford! Not even with me," Mabel added, flailing her arms.

"Well, are you trying to _control my life again_ like you always do?" Dipper questioned, clenching his fists.

" _What_ are you talking about?" Mabel asked, scowling.

"Stop pretending like you're goody two-shoes!" Dipper retaliated, causing Mabel to clinch and turn away.

"I was possessed by a demon just trying to help you get one of your stupid crushes! I gave up on getting Wendy just so you can get a pig! You pushed me into that "closet" to confess to Wendy, nearly killing us when the shape- shifter was there and you didn't allow us to get back in! You nearly destroyed the world not once, but thrice! You pressed the button when I told you not to!" Dipper ranted, storming about the room.

" _I_ nearly destroyed the world? Well, I if I did not, Grunkle Ford would be trapped in that portal and all of Grunkle Stan's efforts would be wasted! I got you back the author of the journal's you idolize so much!" Mabel protested.

"But you went to trust Stan instead of me! I'm your brother! After all I did for you! Not to mention that you caused Weirdmeggadon with your stupidity! I even had to get you out of your fantasy land!" Dipper spat through gritted teeth as he walked away, hands in his pockets.

"Oh, so you're now trying to act like the boss towards your sister! I didn't argue with you when you left me alone just because you wanted to hang out with Grunkle Ford! I even allowed you to accept his apprenticeship and now you say that _I'm_ controlling your life? I thought you promised that we wouldn't end up all stupid! Some brother you turn out to be!" Mabel growled, dashing after her brother.

"Well, maybe I don't _want_ you as my sister just as I don't want Ford as my great-uncle, trying to take over my life!" Dipper snapped, flashing a menacing glance at Mabel before descending the stairs.

Mabel stood rooted to the ground, feeling as if she had been struck by lightning. As Dipper's words sank in, she saw her vision going red as anger flooded her. Without having any second thoughts, she lunged at her twin, causing them to tumble downstairs. Just as they were wrestling, howling at each other, Ford came into the area, wanting to know what was the commotion about.

" _Dipper! Mabel!_ Stop this instant!" Ford demanded, coming over to pull the twins away from one another.

" _Hey,_ it's not my fault! She started it!" Dipper hissed, accusingly staring at Mabel.

" _What? You're_ the one with the _"controlling your life"_ talk! I'm not even sure if you told anybody If you're going out!" Mabel riposted, resisting the urge to punch her brother.

" _Going out?_ Dipper, I already told you that it's late, and you dare _disobey?_ I clearly recalled that I'm you aren't allowed to go out today!" Ford yelled, teeth gritted.

"Ugh! Fine! Whatever you say! I'm going upstairs!" Dipper hollered, ascending the stairs.

"I... I guess I should too," Mabel said, sighing.

"Mabel, are you okay? I know that you attend school instead of learning with Dipper, so I pretty much didn't have time to talk to you that much, even though it's spring break. I'm sorry, " Ford apologised, clasping his hands, looking at his niece awkwardly

After a moment of awkward silence, Mabel shook her head and wordlessly went upstairs. In her room, she locked the door as she shed bitter tears, asking herself if she should really live any longer.

-0-0-

Tears rolled down her cheeks as she re-read the letter over and over. Ford kept trying to console the girl, but she was too overwhelmed by sorrow. As much as she wanted to rip the letter into pieces, she could not deny the bitter fact. Her tears dripped onto Dipper's suicide letter, and they do not know if they could find where Dipper was or if they could save him.

-0-0-

It has been weeks since Dipper went missing but nobody knew where he went. Mabel had searched every book and cranny of Gravity Falls in hopes of finding her brother to no avail. She considered searching a mountain located near the area, but the police had told her that he was not even there and that it was too dangerous for anybody to wander near the location. She wept herself to sleep every night, unable to contain her grief. She kept questioning herself if Bill's curse was behind her brother's disappearance, but she kept praying that Dipper would return. Sometimes, she felt as if he had thought of it before, but just shrugged the feeling off.

However, on that particular day, things had turned a bit obscure for Mabel. She woke up in a room she did not recognise. Puzzled, she looked outside the window, in an attempt to convince herself that nothing was wrong. However, instead of the usual forest surrounding the Mystery Shack, she saw that she was in a bustling city. Eyes widening in horror, she bolted downstairs to find Ford. She indeed found him, but by banging straight into him.

"Mabel, what's the rush? It's only Saturday," Ford reminded as he steadied his niece.

"Grunkle Ford! Where are we? What happened to Gravity Falls? Where's Waddles? Did we secretly move house?" Mabel asked, panicky.

"Mabel, we're at home in Ebott City, remember? Who's Waddles? You moved in with me months ago!" Ford exclaimed.

"Are you feeling alright Mabel? You look pale," he added, glancing a worried look at her.

Mabel was rooted to the ground, dumbfounded. Ebott City? But they were living in Gravity Falls!

"Maybe you're just stressed from school. I was about to call you down for breakfast anyway," the researcher stated.

-0-0-

Mabel wandered around the busy streets of Ebott City, deep in thought. She clearly knew that she was not in the original place she once was. Everything was the same, such as Wendy and Soos, although they were working in a supermarket. The Northwests were living in their mansion, with McGucket, who's appearance had somehow reverted to the one he had before losing his sanity, living as her neighbour. It seems as if the citizens were made out of people from Gravity Falls and some new faces, but they seemed to not recognise her, including Brenda and Candy, her two best friends.

"Well, everything is the same, like the mountain and Dipper remaining missing," Mabel muttered, plopping into a bench located near a huge patch of golden flowers.

Staring at the sky, the girl sighed. She felt as if she had been thrown into an alternate version of her life. Ford does seem to know something, and Mabel could tell from the way he had been writing in his new journal non-stop, although there were no anomalies around. She had went exploring the forest, hoping to find a gnome or some anomaly but it almost seemed like there were none in the area, which was unlike Gravity Falls.

Who am I kidding? Maybe It was all a dream that I was ever in Gravity Falls and Waffles was my imaginary pet, Mabel thought.

Just then, she saw Gideon, her annoying admirer, walking towards her. She groaned as she recalled the nefarious boy's attempts to steal the Mystery Shack and get her as his girlfriend. Pretending not to see him, she hopped off the bench and briskly walked back home.

-0-0-

Mabel knew that she not imagining the changes. A few days later, she had woken up on a bed in a hotel, with nothing she recognised, save for her great-uncle's journal on the bedside table and the scenery of Ebott City outside the window. The moonlight flooded through it, allowing her to read a page that fell out of the journal when she picked it up the day before yet again. In Ford's rushed but near handwriting was written:

 _Dear Mabel,_ _I know you are having a hard time coping with the changes in your environment, but I cannot blame you for it. I myself have been facing troubles with what seems like a change in the timeline. I have went to investigate Mount Ebott as there was another change like our house disappearing as if it had not existed, which was why you are in the hotel. I will return shortly but do take care of yourself._ _Your Great-Uncle,_ _Stanford Pines_

Mabel knew that she was not the only one to realise the sudden change, but in the course of one day living alone, she was beginning to worry. What if Ford was in danger? She recalled Bill's curse and if her great-uncle was alone in the mountain, who would know if anything were to happen to him?

 _Well, maybe I don't want you as my sister!_

Dipper's words rang in her ears, causing tears to well up in her eyes. She was a terrible person, letting Weirdmeggadon happen. She had considered going to the mountain to search for Ford, but what was the point? She knew that everybody was better off without her and her stupidity. She had heard legends of people never returning from Mount Ebott, the mountain not far from the city, which was proven by the newspaper article she had read months ago.

-0-0-

Hours turned to days, leading up to a week. Mabel was sick of the timeline. Ford had yet to return, causing her to be utterly lost. She had no school to go to(the principal, who was Preston Northwest, had snootily told her to leave as outsiders were not allowed in his school for the privilege), she was treated as a freak and was left alone. In addition, she had used up most of her poclet money to pay the rent of the cheap but luxurious hotel.The only things she enjoyed were to sit by the golden flowers and to have tea with Mayor Tyler.

The wind howled ominously, rustling leaves of the trees. Mabel walked through the darkness, wearing a blue sweater with two purple stripes, a brown skirt and her usual shoes with white socks. The rocky mountain was deserted, with no signs of civilisation anywhere. She had hiked up the area for nearly a day with the hope of finding Ford. She smelled fresh earth as she walked along a trail with eight separate trails of footsteps, having the mentality that it would lead her somewhere. She clutched her bag, which held a bottle of water and some necessities, such as an inusufficient roll of bandage and food. A sense of hopelessness hung in the air as thoughts flooded her mind. She held a stick she found, which was particularly stiff. She looked down at it, sighing as a terrible thought came to mind.

A chilling cackle, soft but noticeable, echoed. Mabel turned around, pointing the stock at an absent enemy. She took a few steps back before feeling herself falling back into a hole. Screaming, she tried to grab her trusty grappling book from her bag as the night sky became further and further. White engulfed her as her consciousness slipped away, pain stabbing her mercilessly. Her world went dark as a voice, as clear as day, sounded.

 _Mabel, say determined! You're the future hope of this world!_

-0-0-

A/N: Well, this was dark. Reviews are needed to improve an author's writing style, so please do. Next chapter is being written. Stay determined, readers!

~Lilis


End file.
